Speaker
Description
The main aim of the LHC forward (LHCf) experiment [1] is to provide precise measurements of the particles production rate in the forward region. These high energy calibration data are very important for the tuning of hadronic interaction models used by ground-based cosmic rays experiments. LHC is the most suitable place where we can perform these measurements because a proton-proton collision at $\sqrt{s}$ = 14 TeV is equivalent to the interaction of a $10^{17}$ eV cosmic ray with the atmosphere. In order to do that, two small sampling calorimeters are installed at ±140 m from LHC IP1 (ATLAS Interaction Point), so that they can detect the neutral particles with $\eta$ > 8.4 produced in p-ion collisions [2].
In the past years, LHCf acquired data from p-ion collisions at different energies (p-p at $\sqrt{s}$ = 0.9, 2.76, 7 and 13 TeV; p-Pb at $\sqrt{s_{NN}}$ = 5.02 and 8.1 TeV). In this talk, we would like to present the analysis results relative to photons [3], neutrons [4] and $\pi^{0}$ [5] differential production cross sections, compared with models predictions. In particular, we will discuss the measurement of the energy distributions of secondary particles produced in $\sqrt{s}$ = 13 TeV p-p collisions (photons, already published [6], and neutrons) and in $\sqrt{s_{NN}}$ = 8.1 TeV p-Pb collisions (photons). In all these cases, no model resulted to be in good agreement with experimental observations in all the regions investigated by the analysis. We will also discuss about the ATLAS-LHCf joint analysis, based on the common data taking that the two experiments had in the last two operations at LHC. This activity is very important because the information of the ATLAS detector in the central region is an useful tag to distinguish between diffractive and non-diffractive events in the LHCf detector. Finally, we will present the measurement relative to the contribution of diffractive dissociation to the production of forward photons in $\sqrt{s}$ = 13 TeV p-p collisions [7], the first result from the ATLAS-LHCf joint analysis.
